This invention relates to a device for feeding a consumable wire electrode. The device is provided with two feeding units mounted in tandem, each of the feeding units having a pair of rolls. At least one of the rolls of each pair is a driven one.
Known devices of this kind are provided with feeding units mounted very close one behind the other and driven by the same motor. The motor is coupled to the rolls by gears having such a transmission ratio that the rolls rotate with the same speed. It is necessary that the circumferential speed of the rolls is equal in order to avoid stretching or bunching of the wire between the two feeding units. Therefore the diameter of the driving rolls must be exactly the same.
Other known devices have feeding units driven by individual motors. The speed characteristic of each motor is controlled individually for adjusting the pulling force transferred to the electrode. This requires control circuits for matching the speed characteristics of the motors.